Two semiconductor structures, each including one or more semiconductor devices fabricated on a semiconductor substrate, are interconnected by the brazing connection between a low melting metal buried in a joint aperture and a protrusion of the other semiconductor structure plunged into the low melting metal in the joint aperture.
A conventional semiconductor structure includes a silicon substrate, an interfacial insulation layer formed on the silicon substrate, a conductive layer formed on the interfacial insulation layer, a polyimide resin layer which is provided with an aperture to locally expose the conductive layer formed on the substrate, and an Au/In layer for brazing which is buried in the aperture of the polyimide resin layer.
For fabrication, one or more semiconductor devices are fabricated on the silicon substrates, and are covered by the polyimide resin layer. Then, the aperture is formed through the polyimide resin layer to expose the conductive layer by photo-etching technology using a photo-resist as a photo mask. Next, the Au/In layer is formed on the exposed conductive layer in the aperture and the entire surface of the photo-resist on the polyimide resin layer, and the substrate thus processed is brought into butyl acetate solution, which is inert to the polyimide resin layer and dissolves the photo-resist. As a result, the Au/In layer is stripped from the polyimide resin layer into the butyl acetate solution due to dissolving the photo-resist, so that the semiconductor structure is fabricated to have the Au/In layer burying the aperture.
According to the first conventional semiconductor structure, however, there are disadvantages in that the stripped Au/In layer may be adhered to the surface of the polyimide resin layer, when the substrate is lifted off the butyl acetate solution, so that the fabrication yield is decreased. Further, the fabrication of semiconductor structures becomes high in cost, because the Au/In layer is inevitably formed on the entire surface of the polyimide resin layer layered by the photo-resist. In addition, when the Au/In layer is heated for brazing, the melted Au/In is diffused to the interface between the conductive layer and the polyimide resin layer.
The conventional semiconductor structure may have a modified structure in which a top surface profile having a lift portion is defined to accommodate a semiconductor device thereunder.
According to the modified conventional semiconductor structure, however, there is a disadvantage in that an aperture passing through a polyimide resin layer must be deeper, because the polyimide resin layer is thicker on non-lift portion. As a result, the Au/In material is increased in amount, so that the fabrication of the structure becomes high in cost.